Priedrich gustav adolf heller



(No Model.)

F. G. A. HELLER. FILAMENT FOR INOANDESGENTYELEOTRIG LAMPS.

Patented Mar. 24,1891.

W H n w 0 C A Lavmr:

57 WW I wrzw y.

Witnesses m: mums versus co., vnonrumc wumnaron, n. c:

" emitting layer cohere very strongly, while a NITTED STATES PATENT FRIEDRICH GUSTAV ADOLF HELLER, OF BERLIN, GERMANY, ASSIGNOR TO SIEMENS & HALSKE, OF SAME PLACE.

FILAMENT F OR INCANDESCENT ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent No. 448,920, dated March 24, 1891.

Application filed July 22 1890. Serial No. 359,544:- (No model.)

To all whom it may concern.-

Be it known that I, FRIEDRICH GUSTAV ADOLF HELLER, engineer, a subject of the King of Saxony, residing at Berlin, in the Kingdom of Prussia and German Empire, have invented certain new and useful Improvements in Filaments for Electric Glow-Lamps; and I'do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The most frequent method of manufacturing filaments for electric lamps consists in causing the common carbon filaments taken from the furnace to glow within an atmosphere of some hydrocarbon, causing thereby carbon to be deposited upon the filaments. These filaments suffer from certain defects the diminution of which is desirable. One defect, for instance, is that the carbon layer deposited is eventually removed through the influence of the current, so that the filament gets useless after a certain time. Another great defect. in this method of manufacture arises from the fact that the carbon layer deposited, being of extremely good conducting capacity, considerably diminishes in consequence the resistance of the carbon filament, necessitating the use of Very thin carbon filaments and very thin layers of deposited carbon in order to obtain a glowing substance of conveniently high resistance. My method of manufacturing glowing substance reduces considerably the said defects. The hereinafter-described filament has the property that the particles forming the light far more feeble tendency exists to disperse the layer, and the whole inner cohesion of the glowing substance as compared with the destroying influences is considerablystronger. This new body is for practical purposes best manufactured in filament shape, as shown in the figure of the drawing.

First a filament must be got of a convenient carbonizable matter, and then be put in proper shape. After this the filament is carbonized in a furnace for that purpose in the common way. The proportions and resist ances of these filaments are chosen and de termined according to requirements.

It has been found that if carbon filaments prepared in the afore-described manner be covered with a layer of such metals which melt only with difficulty and whose melting-point is high enough to allow them to resist easily to such temperatures as occur in incandescent lamps, the cohesion of these particles with the inner filaments, and at the same time between themselves, will be a strong one. This cohesion makes itself felt against the influences attacking the durability of a filament made to glow by a passing current, as well as against those influences which eventually bring about the dispersion of the particles and their settling on the glass bulbs. As metals proper for the purpose may be mentioned chromium and others of simi lar properties. Chromium I have found to give the most satisfactory results under the various conditions to which the filaments are subjected. The filament so formed is not liable to be easily fractured, as is the case with many of those now in use, and gives an excellent light.

The metallic cover may be obtained in different manners, either by the purely electrolytioal way, in which the carbon filament forming the inner part of the glowing body acts as one electrode, or by the direct chemical waythrough reduction of a metallic salt put upon the carbon filament by any proper means of reduction.

It depends entirely upon the proper use of the method to give to the metallic cover more or less conducting capacity, and it has been found that the filaments which resist well the influences tending to dispersion have a metallic layer of a comparatively high specific resistance. In the described manner of combining a carbon filament with a layer of a metal fusible with difficulty may be obtained filaments of comparatively high resistance, which, without being of too attenuated proportions, offer considerably more durability than the hitherto known filaments, and possess, further, at high temperature far less capacity to disperse their particles, and by their 2. A filament composed, essentially, of carpurely metallic surface favor very greatly the hon and chromium,substantially as described. production of light. In testimony whereof I have aflixed my sighat I claim, and desire to secure by Let nature in presence of two Witnesses. 5 ters Patent, is

1. A filament for electric lamps, consisting, FRIEDRICH GUSTAV ADOLF HELLER essentially, of a small carbon rod or core with a covering of metallic chromium deposited WVitnesses: upon the outside thereof, substantially as de- GEORG ELWEIN, [O scribed. MAX WAGNER. 

